use std::env;
use std::fs;
use std::process;
use std::error::Error;

pub struct Config {
    query: String,
    filename: String,
    pub case_sensitive: bool,
}

impl Config{
    pub fn new(args: &[String]) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("not enough arguments");
        }
        
        let query = args[1].clone();
        let filename = args[2].clone();
        
        // 检查环境变量
        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();

        Ok( Config { query, filename ,case_sensitive } )
    }
}

pub fn parse_config(args : &[String]) -> Result<Config, &'static str>{
    Config::new(args)
}
//Box<dyn Error>是智能指针
pub fn run(config : Config) -> Result<(), Box<dyn Error>>{
    
    let contents : String = fs::read_to_string(config.filename)?;

    let results = if config.case_sensitive {
        search(&config.query, &contents)
    } else {
        search_case_insensitive(&config.query, &contents)
    };


    for line in results{
        println!("{}",line);
    }

    Ok(())
}

pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let mut result = Vec::new();
    for line in contents.lines(){
        if line.contains(query){
            result.push(line);
        }
    }
    result
}

pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let query = query.to_lowercase();
    let mut result = Vec::new();
    for line in contents.lines(){
        if line.to_lowercase().contains(&query){
            result.push(line);
        }
    }
    result
}

//分开的好处就是方便编写测试
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn one_result() {
        let query = "duct";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.";

        assert_eq!(
            vec!["safe, fast, productive."],
            search(query, contents)
        );
    }

    #[test]
    fn case_sensitive() {
        let query = "duct";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Duct tape.";

        assert_eq!(
            vec!["safe, fast, productive."],
            search(query, contents)
        );
    }

    #[test]
    fn case_insensitive() {
        let query = "rUsT";
        let contents = "\
Rust:
safe, fast, productive.
Pick three.
Trust me.";

        assert_eq!(
            vec!["Rust:", "Trust me."],
            search_case_insensitive(query, contents)
        );
    }
}